JDS ATOM 2 Review: Behold! The Increased Power Of ATOM!!

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Big Thank You to John Seaber and Jude Hopper over at JDS for their, and their team’s, continued support of the blog and channel over the years. The ATOM 2 was sent to me free of charge in exchange for an honest review.

Greetings mate and Welcome aboard!

Stuart Charles here, HomeStudioBasics.com helping YOU make sound decisions, so…

Since 2018, the ATOM has been JDS’ main entry-level desktop Amplifier, succeeded by the one and only Objective 2, which, in some ways, I still miss dearly (because nostalgia and stuff).

That said, the ATOM has seen a couple of revisions since the earliest iteration, with ATOM AMP 2 being the latest induction into JDS’ discerning lineup of products.

Valuing quality over quantity, the Collinsville, IL-based company, founded in 2007, continues to be the benchmark of excellence within the Amp/DAC realm.

Related: What Is a Headphone Amp? Demystifying the Sound Experience

Today we’ll review the ATOM 2 and learn more about what sets it apart from its predecessors – discussing things like its build quality, power output, output impedance, sound characteristics, and more.

This writeup will act as both a review and shootout, as we compare and contrast the OG Atom Amp, Atom Amp+ “Hevi” and Atom 2.

By the time you’re finished reading this article, not only will you know whether or not the ATOM 2 is for you, but you’ll also know exactly why I respect this company head and shoulders above everyone else.

So grab a snack, sit back and relax. You’re in the right place.

What Is It?

The ATOM 2 is a standalone headphone amplifier and preamplifier rolled into one.

It can be used as an amp for your headphones or a preamp with separate active speakers like the Presonus Eris e3.5.

Because it is standalone, you’ll need a DAC to pair with it. I’d recommend JDS’ own ATOM DAC 2 and some RCA to RCA cables.

The ATOM DAC 2 has RCA outputs, a USB-C jack for your PC, and an optical input for console gaming (or whatever else you want).

Build & Aesthetic

One of the main differences between the Atom Amp+ HEVI and ATOM 2 vs. the original ATOM is the build quality.

Long story short, the upfront costs of manufacturing injection-molded enclosures for the original ATOMs, while quick and efficient, cost a small fortune and were difficult to transport due to weight.

These initial setup costs were prohibitive for lower volume designs as it was much harder to recoup the expenditure.

This is one reason why the Atom line is Amp and DAC only.

In any event, the Atom Amp+ HEVI improved on the flimsy nature of the OG ATOM (Referred to as Atom Amp+) by making it heavier and more robust.

Outside of those differences, everything else was identical.

As for performance, Atom Amp+ Hevi is built on the same circuit board as Atom Amp+, so all published specifications are still valid. “Hevi” is purely a mechanical upgrade.John Seaber, JDS Labs

Interestingly enough, JDS’ transition to an all-aluminum chassis also caught a snag when the original engineering samples rattled unacceptably (as they put it).

Because of this, a separate version was prototyped in the interim, and, due to a manufacturing delay of the metal chassis, they decided to release this surprisingly good “Hevi” model while waiting.

So just think of the Hevi as a stopgap of sorts. In other words, all HEVI editions are being replaced by Atom Amp 2 and Atom DAC 2.

Speaking of, the Atom Amp 2 is all metal, housed in an aluminum chassis, and features an easier-to-grip knob in addition to an anodized surface.

If you were unaware, an anodized surface refers to a protective layer created through an electrochemical process on materials like aluminum, enhancing durability, corrosion resistance, and allowing for the application of colors/engravings while maintaining the material’s essential properties.

And yeah, it’s even more robust than the ATOM Hevi (pictured above), coming in at a substantial 461g. The Hevi, while solid, is only 436g. The OG ATOM, if you can believe it, was only 263!!

Note: These numbers may vary slightly based on the scale used.

You’ll also notice the ATOM 2 is ever so slightly larger in both length, width, and height, to the tune of less than a 1/4″ but still fairly noticeable when you stack ’em.

For reference, the ATOM 2 is a clean 5″ x 5″ x 1.25″ per my measurements.

Front Panel

The front, from right to left, contains your input button, gain button, volume potentiometer, a 1/4″ (6.35mm) headphone jack, and a 4.4mm jack.

The 4.4mm headphone jack on the Atom Amp 2 might spark curiosity among users wondering if it operates in a truly balanced mode.

Addressing this, it’s important to note that the 4.4mm jack doesn’t employ a differential bridged mode circuit, commonly associated with fully balanced outputs, to achieve doubled voltage swing despite the potential increase in noise and total harmonic distortion (THD).

However, what it does offer is quite impressive. Testing reveals that both headphone jacks of the Atom Amp 2 deliver a substantial 26 volts peak-to-peak (Vpp) in a single-ended mode, showcasing a remarkably low noise floor.

Despite not being a fully balanced output, the 4.4mm jack demonstrates commendable performance with substantial voltage output and minimal noise interference, catering to enthusiasts seeking high-quality audio experiences.

To listen, first connect the unit to wall power via the supplied Dummy thicc wall wart.

Then, connect your DAC using the outputs and plug the other ends into the ATOM using RCA or 3.5mm line inputs. The DAC will be connected to your PC via the USB-C slot. It also comes with a Power Brick.

For connection to your PC, you can use a USB-C to USB-C (if your PC has one), or a standard USB-C to USB-A.

Turn the Volume Pot and you’ll see a white halo light indicating power is present.

Press the input button for a 3.5mm line in connection, and release it for RCA.

If you want to use the ATOM as a preamp into separate speakers, just run RCA to RCA or RCA to line from the outputs on the ATOM into your speakers of choice.

Then simply unplug your headphones and the sound routes through the speakers.

To switch back, plug your headphones in again.

Back Panel

JDS ATOM 2 (Top), ATOM Amp+ Hevi (Bottom)

The back is the same, only they gave it a much more professional look by having all of the jacks seated in a recessed position, providing a more secure and stable placement while reducing the risk of accidental damage or disconnection.

In addition, you’ll notice the Atom Amp 2’s RCA Inputs now physically align with Atom DAC 2’s RCA Outputs.

If you’ll recall, the Outputs of the earlier ATOMs were situated to the right. Now they are on the left.

If all that wasn’t enough, they also improved the specs. Let’s take a look.

Features and Versatility

If for whatever reason you were worried about power output in previous models, the ATOM 2 hits you with double the juice of the Atom Amp+, coming in at an astonishing 2.65W (9.22VRMS) of continuous power @ 32Ω, and 143mW (9.28VRMS) @ 600Ω.

Recommended: RMS Power vs. Peak Power In Headphone Amplifiers

For reference, the Atom Amp+ pumped out 1W @ 32Ω and 136mW @ 600Ω.

I can surely pontificate on this until the cows come home, but I’ll save you the rant. I’ll just say that even 1W was more than enough, and JDS has been saying the same thing for many years.

That said, it’s nice that they took the time to improve the specs regardless, as Signal-To-Noise Ratio, Intermodulation Distortion, Dynamic Range, and Overall Noise Floor are all slightly improved.

Octo Buffers

To increase power without taking up more space, JDS replaced the large, single LME49600 buffer with numerous, less powerful buffers which ultimately achieved the same result.

Parallel buffers also happen to cancel out some common mode noise, which, as mentioned above, reduces the noise floor.

From JDS:

We evaluated several variations of paralleled output buffers. Atom Amp 2 was originally drafted with 4x OPA1692s per channel, due to their low quiescent current (cooler running). The setup achieved less output power than Atom Amp+, so doubling the number of buffers to 8x would improve the situation. By chance, OPA1692s were out of stock at the time of the octo-buffer prototype build. Our prototyping service suggested OPA1656s as an alternative, and the change stuck. Octo-OPA1656s deliver 75% more power than OPA1692s. Atom Amp 2’s THD performance is exceptional and power is extreme. You can turn the volume knob to 100% with 32Ω headphones and hear perfectly clear music at 9.22VRMS = 26Vpp = 2.65W.
There is no incentive to move beyond octo-buffers, now that power is limited by voltage swing. Audio opamps are typically limited to +/- 18V rails before self-destructing, and it’s good practice to leave some safety margin. Redesigning around a differential output topology is the only way to push power dramatically higher in a solid state amp, but differential outputs have their own tradeoffs (more noise, higher THD).JDS Labs

Output Impedance & Sound

Playlist: Here!
Headphones Used: Gold Planar GL2000 (4.4mm), HIFIMAN HE400se (4.4mm), AKG K702 (6.35mm), HIFIMAN Arya (4.4mm), HarmonicDyne G200 (4.4mm). More to come.
DAC(s) Used: AudioQuest DragonFly Red, iFi Zen, Zen V2, FiiO K7.

Perhaps the most important consideration (along with Signal-to-noise ratio) when evaluating the “sound” of an Amp lies in its Output Impedance number.

Recommended: What is Output Impedance?

A low number (close to zero) ensures that the amp will always deliver the same (or roughly the same) output into any load.

In simpler terms, it means the amp is a consistent performer with a variety of headphones and Impedances.

As with various types of audio electronics, if you have an output impedance that is too high, it can have a filtering effect.

This causes anomalies in the frequency response as well as diminished power output.

The ATOM 2 avoids this by utilizing a number less than 1, ensuring incredibly accurate and transparent audio with any headphones you may have.

One small difference this time is that the ATOM 2’s is indeed exactly 0.7Ω, while the original was advertised as <0.7Ω.

Again, a difference you’ll never be able to hear in passing.

So, the sound?

It continues JDS’ tradition of clean, neutral, and transparent output which in the eyes of many, is essential for a fantastic listening experience.

Regarding transparency, it might be subjective, but I’ve consistently noticed that JDS products notably enhance the feeling of being present in the studio space alongside the artists.

I’ve previously discussed this when referring to the Objective 2, and I’ve had a similar experience with the various ATOM models paired with an array of headphones; one such headphone being the HIFIMAN Arya.

While most of these sensations are owed to the Arya’s impressive sense of separation and superior resolution compared to mid-range headphones, the ATOM adds that extra touch.

You’ll begin to discern numerous details within the recording, offering a glimpse of the actual space and capturing every subtle sound and atmospheric nuance the artist incorporated into the song.

However, this effect is contingent upon the track and its recording method.

For example, Frou Frou’s “Hear Me Out” is so well mastered, so clear and detailed, that it makes me want to cry. It just sounds sublime.

I never noticed the nuance in the opening drum hits before the snare comes in.

At around 24 seconds when the beat drops, you can hear this kind of subtle supporting snare, in addition to the main one. It sits in the background, and kind of sounds a bit hollowed out and dry.

In addition, her vocals sound so much closer and more intimate. You can hear all the subtle inflections of her voice, as her delicate, somewhat frail nature comes through so well that you may, for a split second, have a hard time not believing she’s in the vicinity.

If all that wasn’t enough, every lyric is easily distinguished, contributing to the amazing resolution of the Arya and neutral profile of the ATOM.

Simply put, it’s a match made in heaven, immersing you in the music all the more.

Now, apply this one example to hundreds of tracks you think you know like the back of your hand, and you can easily figure out why some people end up going down the rabbit hole never to return ever again.

Here’s me going down said rabbit hole:

Potential Downsides

While having an amplifier like this is appealing, it’s essential to note some drawbacks.

One significant reason why low output impedance isn’t universally ideal relates to variations in the source quality—essentially, how well the music was recorded, mixed, and mastered.

If the source quality is subpar, an amp like the ATOM, combined with your headphones, will vividly expose these flaws, potentially leading to an unpleasant experience depending on individual preferences.

Conversely, at times, this can enrich the experience, allowing appreciation for peculiar errors or anomalies in the track—something I personally find enjoyable.

It brings a freshness to the music listening experience, often revealing new elements in older tracks that had faded from memory.

You may also find yourself thinking or saying out loud something like “What the heck is going on?”

Things may not sound quite right until you realize that you’re starting to hear all the small morsels and grains you missed before with other dog food headphones.

These types of subtleties can range anywhere from guitar plucks, fingers sliding down the fretboard, breathy/throaty sounds, background soundscapes, general wispy ambiance, additional instruments you may have missed, backing vocals that sound clearer and more distinct, a dog barking, someone pooping, you name it.

In essence, tube amps tend to conceal errors and subtle imperfections in recordings, whereas solid-state amps like the ATOM 2 certainly do not, offering a more transparent playback of the original recording.

Related: Ranking Tubes And Tube Hybrids

Overall Value & Final Verdict

The Atom Amp 2 continues JDS’s tradition of crafting fantastic headphone amplifiers, and, with the inclusion of the 4.4mm output, improved specs, and upgraded build, it’s an even better value now and remains a Gold Standard for entry-level audio.

The fact that they did all this for only $30 more, in addition to their unwillingness to make loads of unnecessary amps at varying ridiculous price points, only further reinforces how much respect I have for the company.

With that, are you ready to make the ATOM yours?